Crushing Principles of Mechanical Crushing

8/17/2019 Crushing Principles of Mechanical Crushing

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Crushing- Principles of Mechanical Crushing


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Per Svedensten

Manager Crushing Chamber and

Materials Development

Product Development Center

Crushing (R&D)

Master of Science in Mechanics,

specialized in mechatronics

Ph.D 2007, Chalmers Universi ty

Partly funded by Sandvik

Modeling, simulation and

optimization of crushing plants

Technical-EconomicOptimization

Sandvik employee since 2004


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Objective

Explain the interactionbetween

rock material

and

crusher


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Take home messages


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Agenda

Cone Crusher Operating Principal

Crusher Operation

Rock Breakage Behavior

Crushing Forces

Optimization and Crusher Performance Map Conclusions

NCC, Borås, Sweden


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I m pl em en t a t i on s

Scientific Approach

Hypothesis / System behavior

Prediction of performance

Utilize results for improvement

Choice of method and/or modeling

Study and/or prediction of system behavior

Verification

Problem / Research Question

Customer Values


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Cone Crusher

Why Cone Crusher?

The cone crusher designconcept is an effective and smartway of realizing compressive

crushing Aggregate Production

Mechanical Liberation ofValuable Minerals


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Product

Feed

Power

Operating Principle

Heat

Noise

Lube

Oil

Hydraulic


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Operating Principle


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Operating Principle


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Operating Principle


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Operating Principal

Opening Phase == Transport

Closing Phase == Crushing


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Transport

Crushing

Mantle

Concave

Operating Principal


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Operating Principal

10 Indentations


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Crushing

Mantle

Concave

Operating Principal

Transport


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Mantle

Concave

Crushing

s

b

b: Bed Height

s: Compression

s/b: Compression Ratio

Operating Principal

Crushing Zone


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Mantle

Concave

Single Particle Breakage SPB

Inter Particle Breakage IPB

Operating Principal


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Operating Principal

In a cone crusher the stones are crushed with both SPB and IPB as thematerial moves down through the chamber.

The relative amounts of IPB and SPB depends on factors like chamberdesign, crusher geometry, speed, css, eccentric throw, and others.

SPB IPB

Fines Less More

Shape Flaky Cubic

Force Low High


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Operating Principal Capacity

Cross section area

0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

i

Area [m2]

Area function

Choke level


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Operating Principals

0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

Nominal Cross-Sectional Area

Y - c o o r d i n a t e [

m ]

Area [m2]

Choke level

Choke zone

Capacity


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Operating Principals

Standard


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Crusher operation

As the market demand shifts can the crusher operation be modified?

The crusher is likely to be installed for maximum production. Can it bechanged to maximum efficiency?

Understanding how breakage and capacity is effected by Eccentric Throw

Speed

Closed Side Setting


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Crusher operation

Running the crusher at different eccentric throws

ECC 0.6” (16 mm)51 tph

ECC 1.0” (25 mm)75 tph

ECC 1.4” (34 mm)97 tph

-0.08”: 16%

0.08”-0.5”: 80%+0,5”: 4%Fines/Product: 0.20

-0.08”: 19%

0.08”-0.5”: 74%+0,5”: 7%Fines/Product: 0.25

-0.08”: 20%

0.08”-0.5”: 73%+0,5”: 7%Fines/Product: 0.27


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Crusher operation

Running the crusher at different eccentric throws, CSS optimized

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

16 36

P r o d u c t i o n [ % ]

ECC [mm]

Product

Fines

Re-circulation


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Crusher operation

Running the crusher at different speeds

280 rpm106 tph

360 rpm104 tph

440 rpm96 tph

-0.08”: 13%

0.08”-0.5”: 69%+0,5”: 18%Fines/Product: 0.19

-0.08”: 17%

0.08”-0.5”: 71%+0,5”: 12%Fines/Product: 0.24

-0.08”: 21%

0.08”-0.5”: 71%+0,5”: 8%Fines/Product: 0.30

Changing speed can have mechanical effects on the crusher and motor


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Chamber DesignDesign drawings

FineCoarse


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Crusher operation


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Crusher operation

Chamber selection

Fine Medium Coarse Extra Coarse


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Crusher Operation

Relation between CSS andShape

The size were the best shapecan be found is at CSS

It is very difficult for cubicalstones larger then CSS to passthe chamber

Breakage of stones creates flakyparticles. Smaller flaky stoneswill more easily find its way

through the chamber

F a

n e s s

n e x [ % ]

Particle size [mm]

Increasing CSS


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Crusher Operation

Relation between Feed size andShape

The greater reduction ratio theworse particle shape.

Inter particle breakage improvesshape. When crushing a bed ofmaterial weaker particles willbreak first. Flaky or elongatedparticles are weaker then round.

Breaking round particles gives

flaky material.

F l a k i n e s s i n d e x [ % ]

Particle size [mm]

Increasing average feed size x


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OptimumCSS

Reduction

Crusher Operation


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Process Capacity

Design capacity: 200 tph

Crusher Capacity: 300 tph

Choke fed Crusher operation(300 tph):

Material in surge bin runs out at evenintervals

Consequence:

Crusher is operated choke fed 66% oftotal operating time feeding the screen

with 300 tphScreen overload

Solution: Adjust throw in order to reach200 tph capacity

32

200

200

200

66% Capacityutilization

300

300


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SPB IPB

Compression ratio Compression ratioDistribution width

Laboratory investigation of breakage modes

Compressive crushing with hydraulic press.


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Short fraction

Long fraction

Compression ratio

Packing limit

S e l e c t i o n


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Dolerite

Gneiss


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Crushing Force

s

b

b: Bed heights: compression

s/b: compression ratio

F: ForceF = f(s/b, σ )σ: Fraction length

F

F


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Crushing Force

( ) 2 2 2 2 21 2 3 4 5 6, p s a s a s a s a s a s a s

size distribution width

σ σ σ σ σ

σ

ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ

ℵ

= + + + + +

=

Multi (inter) particle

-pressure response Packing!


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Crushing Force

( ) ( )32 1 2, k F s d d k s k s

s compression ratiod particle size

ℵ ℵ ℵ

ℵ

= +

=

=

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

0

500

1000

1500

2000

2500

3000

3500

4000

quartzite 16-19

o tests- simulations

Single particle

-force response

F o r c e

[ N ]

Compression ratio

O ti i ti f Fi l C hi St


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Optimization of a Final Crushing Stage

Who is control of your process

performance? What tools have been provided

to make the production efficient?

Optimi ation of a Final Cr shing Stage


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The crushers are the last sizereduction stage in the valuechain.

Over crushing is common.

The connection between crushersetting and yield is oftenunknown

The rock cannot be repaired.

We need to control the crusher

carefully.

O ti i ti f Fi l C hi St


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Optimization of one parameter(CSS) can be done by samplingand analysis

The invested time and lost

production will quickly be repaidby increased productivity

Combine product yield andeconomic aspects

This can be done by taking

samples and making theanalysis in MS Excel

Planning Sampling Analysis Optimization


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Run the crusher at different settings

Take at least one sample at eachsetting. (Multiple samples are oftenuseful)

Special Attention to Safety when takingsamples!!

Position of point were samples aretaking.

Ensure that the conveyor will not start byaccident.




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Particle Size Distribution Plots

If taking single samples on eachCSS the risk of getting

inconsistent results might makethe graph look strange.

Impossible to determine optimumsetting by only using particle size

distribution graphs




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If taking single samples on eachCSS the risk of gettinginconsistent results might make

the graph look strange.

Impossible to determine optimumsetting by only using particle sizedistribution graphs




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0

10

2030

40

50

60

70

80

90100

0.001 0.01 0.1 1 10

p e r c e n t p a s s i n g

sieve size ['']

Particle Size Distribution at CSS 0.79''

0,79


0

50

100

150

200

250

0.50 0.60 0.70 0.80 0.90 1.00

C a p a c i t y [ t p h ]

CSS ['']

Capacity and CSS


Combine the particle size distribution and capacity.

Percentage of final product times the capacity gives the production capacity ofeach product.

Example 0.08’’-0.16’’ mm at CSS 0.79’’:

Percentage of crusherproduction

20% - 11% = 9%

Crusher capacity

193 tph

Total Production:

193 tph x 9% = 17 tph



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Entering all the values into MSExcel makes this easy to getproduction capacities.

Still difficult to determine theoptimal setting




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Use the price* per ton for allproducts:

0-0.08’’: $ 0 (by-product)

0.08-0.16’’: $ 12.30

0.16-0.32’’: $ 13.85

0.32-0.64’’: $ 16.90

0.64-0.87’’: $ 10.80

Make an income graph bycombining prices with capacity


*All prices are estimates based on publicly available data



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What difference does it make?

Running the crusher 0.08’’ off:

Decrease the profit by 58.5 $/h

Running the crusher at 1600hours per year:58.5*1600=$93600


Crusher Performance Map


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Crushing Principles of Mechanical Crushing

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